func MergeFiles(dest string, sources ...string) error {
merged, err := pdf.Create(dest)
if err != nil {
return fmt.Errorf("create %q: %v", dest, err)
}
// because pdf files are mmap'ed and objects are zero copied
// the files must remain open until merged is saved
closers := make([]io.Closer, 0, len(sources))
defer func() {
for _, c := range closers {
_ = c.Close()
}
}()
// add the contents of each pdf into the merged pdf
// collects the roots of each pdf
roots := make([]pdf.ObjectReference, 0, len(sources))
for _, fn := range sources {
file, err := pdf.Open(fn)
if err != nil {
return fmt.Errorf("open %q: %v", fn, err)
}
closers = append(closers, file)
_, root, err := copyReferencedObjects(map[pdf.ObjectReference]pdf.ObjectReference{}, merged, file, file.Root)
if err != nil {
return err
}
roots = append(roots, root.(pdf.ObjectReference))
merged.Root = root.(pdf.ObjectReference)
}
// get the catalogs for each of the pdfs for merging their contents
catalogs := make([]pdf.Dictionary, 0, len(roots))
for _, root := range roots {
catalogs = append(catalogs, merged.Get(root).(pdf.Dictionary))
}
// merge the page trees
pageTreeRef, err := mergePageTrees(merged, catalogs)
if err != nil {
return err
}
// create a new root
merged.Root, err = merged.Add(pdf.Dictionary{
"Type": pdf.Name("Catalog"),
"Pages": pageTreeRef,
})
if err != nil {
return err
}
return merged.Save()
}
func appendPDF(newPDFfilename string, filenames []string) {
merged, err := pdf.Create(newPDFfilename)
if err != nil {
log.Fatalln(err)
}
// add the contents of each pdf into the merged pdf
// collects the roots of each pdf
roots := make([]pdf.ObjectReference, 0, len(filenames))
for _, filename := range filenames {
file, err := pdf.Open(filename)
if err != nil {
log.Fatalln(err)
}
// because pdf files are mmap'ed and objects are zero copied
// the files must remain open until merged is saved
defer func() {
err := file.Close()
if err != nil {
log.Fatalln(err)
}
}()
_, root := copyReferencedObjects(map[pdf.ObjectReference]pdf.ObjectReference{}, merged, file, file.Root)
roots = append(roots, root.(pdf.ObjectReference))
merged.Root = root.(pdf.ObjectReference)
}
// get the catalogs for each of the pdfs for merging their contents
catalogs := make([]pdf.Dictionary, 0, len(roots))
for _, root := range roots {
catalogs = append(catalogs, merged.Get(root).(pdf.Dictionary))
}
// merge the page trees
pageTreeRef := mergePageTrees(merged, catalogs)
// create a new root
merged.Root, err = merged.Add(pdf.Dictionary{
"Type": pdf.Name("Catalog"),
"Pages": pageTreeRef,
})
if err != nil {
log.Fatalln(err)
}
err = merged.Save()
if err != nil {
log.Fatalln(err)
}
}
// create the minimal file described in H.2
func createMinimalFile() {
log.Printf("createMinimalFile")
minimal, err := pdf.Create("h7-minimal.pdf")
if err != nil {
log.Fatalln(errgo.Details(err))
}
defer minimal.Close()
minimal.Root = pdf.ObjectReference{ObjectNumber: 1}
// catalog
minimal.Add(pdf.IndirectObject{
ObjectReference: pdf.ObjectReference{ObjectNumber: 1},
Object: pdf.Dictionary{
pdf.Name("Type"): pdf.Name("Catalog"),
pdf.Name("Outlines"): pdf.ObjectReference{
ObjectNumber: 2,
},
pdf.Name("Pages"): pdf.ObjectReference{
ObjectNumber: 3,
},
},
})
// outlines
minimal.Add(pdf.IndirectObject{
ObjectReference: pdf.ObjectReference{ObjectNumber: 2},
Object: pdf.Dictionary{
pdf.Name("Type"): pdf.Name("Outlines"),
pdf.Name("Count"): pdf.Integer(0),
},
})
// pages
minimal.Add(pdf.IndirectObject{
ObjectReference: pdf.ObjectReference{ObjectNumber: 3},
Object: pdf.Dictionary{
pdf.Name("Type"): pdf.Name("Pages"),
pdf.Name("Kids"): pdf.Array{
pdf.ObjectReference{
ObjectNumber: 4,
},
},
pdf.Name("Count"): pdf.Integer(1),
},
})
// page
minimal.Add(pdf.IndirectObject{
ObjectReference: pdf.ObjectReference{ObjectNumber: 4},
Object: pdf.Dictionary{
pdf.Name("Type"): pdf.Name("Page"),
pdf.Name("Parent"): pdf.ObjectReference{
ObjectNumber: 3,
},
pdf.Name("MediaBox"): pdf.Array{
pdf.Integer(0),
pdf.Integer(0),
pdf.Integer(612),
pdf.Integer(792),
},
pdf.Name("Contents"): pdf.ObjectReference{
ObjectNumber: 5,
},
pdf.Name("Resources"): pdf.Dictionary{
pdf.Name("ProcSet"): pdf.ObjectReference{
ObjectNumber: 6,
},
},
},
})
// content stream
minimal.Add(pdf.IndirectObject{
ObjectReference: pdf.ObjectReference{ObjectNumber: 5},
Object: pdf.Stream{
Dictionary: pdf.Dictionary{
pdf.Name("Length"): pdf.Integer(0),
},
},
})
// procset
minimal.Add(pdf.IndirectObject{
ObjectReference: pdf.ObjectReference{ObjectNumber: 6},
Object: pdf.Array{
pdf.Name("PDF"),
},
})
minimal.Root = pdf.ObjectReference{ObjectNumber: 1}
err = minimal.Save()
if err != nil {
log.Fatalln(errgo.Details(err))
}
}
